Communication system, control device, communication method, control method, and control program

Abstract

A network system (1) comprises a node (10a), a node (10b), a node (10c), and an optical network controller (20). Node (10a) uses a key (K1) to encrypt data to be transmitted to node (10b). Node (10b) uses key (K1) to decrypt data received from node (10a) and uses a key (K2) to encrypt data to be transmitted to node (10c). Node (10c) uses key (K2) to decrypt data received from node (10b). The optical network controller (20) combines an encrypted link (L1) between node (10a) and node (10b) and an encrypted link (L2) between node (10b) and node (10c) and thereby sets an encrypted communication path from node (10a) to node (10c).

Description

COMMUNICATION SYSTEM, CONTROL DEVICE, COMMUNICATION METHOD, CONTROL METHOD, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM

[0001] The present disclosure relates to a communication system, a control device, a communication method, a control method, and a non-transitory computer-readable medium.

[0002] In recent years, communication over networks such as the Internet has become increasingly exposed to various threats, creating a demand for technologies that can ensure secure communication. For example, research into quantum cryptography is underway as an encryption technology to ensure the security of communication.

[0003] Quantum cryptography enables secure sharing of encryption keys between points by quantum key distribution (QKD). Related techniques are known, for example, from Non-Patent Document 1.

[0004] Telecommunications Technology Committee, "JT-Y3800 Overview of Quantum Key Distribution Networks," Version 1.1, June 11, 2021, [online], Internet<https: / / www.ttc.or.jp / application / files / 6516 / 2676 / 5146 / JT-Y3800v1.1.pdf>

[0005] As described in Non-Patent Document 1, a network system that shares encryption keys by quantum key distribution and performs encrypted communications is premised on end-to-end sharing of encryption keys by key relay via relay nodes. Since key relay requires key management and key relay control, it is desirable to perform encrypted communications without key relay.

[0006] In view of these problems, the present disclosure aims to provide a communication system, a control device, a communication method, a control method, and a non-transitory computer-readable medium that are capable of performing encrypted communication without key relay.

[0007] The communication system according to the present disclosure comprises first, second, and third communication devices, and a control device that controls the first, second, and third communication devices, wherein the first communication device comprises a first encryption means that encrypts data to be transmitted to the second communication device using a first key shared with the second communication device, the second communication device comprises a first decryption means that decrypts data received from the first communication device using the first key, and a second encryption means that encrypts data to be transmitted to the third communication device using a second key shared with the third communication device, the third communication device comprises a second decryption means that decrypts data received from the second communication device using the second key, and the control device comprises a setting means that connects a first encryption link between the first encryption means and the first decryption means and a second encryption link between the second encryption means and the second decryption means to set an encrypted communication path from the first communication device to the third communication device.

[0008] The control device of the present disclosure is a control device that controls first, second, and third communication devices, and includes an acquisition means that acquires information regarding a link connecting the first communication device and the second communication device and information regarding a link connecting the second communication device and the third communication device, and a setting means that, based on the acquired information, combines a first encrypted link that performs encrypted communication between the first communication device and the second communication device using a first key, and a second encrypted link that performs encrypted communication between the second communication device and the third communication device using a second key, thereby setting an encrypted communication path from the first communication device to the third communication device.

[0009] The communication method disclosed herein is a communication method in a communication system including first, second, and third communication devices and a control device that controls the first, second, and third communication devices, wherein the first communication device encrypts data to be transmitted to the second communication device using a first key shared with the second communication device, the second communication device decrypts data received from the first communication device using the first key, encrypts data to be transmitted to the third communication device using a second key shared with the third communication device, and the third communication device decrypts data received from the second communication device using the second key, and the control device connects a first encryption link that performs encrypted communication between the first communication device and the second communication device using the first key and a second encryption link that performs encrypted communication between the second communication device and the third communication device using the second key, thereby establishing an encrypted communication path from the first communication device to the third communication device.

[0010] The control method disclosed herein is a control method for controlling first, second, and third communication devices, which acquires information regarding a link connecting the first communication device and the second communication device and information regarding a link connecting the second communication device and the third communication device, and based on the acquired information, combines a first encrypted link that performs encrypted communication between the first communication device and the second communication device using a first key, and a second encrypted link that performs encrypted communication between the second communication device and the third communication device using a second key, thereby setting up an encrypted communication path from the first communication device to the third communication device.

[0011] A non-transitory computer-readable medium storing a control program according to the present disclosure is a non-transitory computer-readable medium storing a control program for causing a computer to execute a process of controlling a first, second, and third communication device, acquiring information regarding a link connecting the first communication device and the second communication device and information regarding a link connecting the second communication device and the third communication device, and based on the acquired information, combining a first encrypted link that performs encrypted communication between the first communication device and the second communication device using a first key and a second encrypted link that performs encrypted communication between the second communication device and the third communication device using a second key, thereby establishing an encrypted communication path from the first communication device to the third communication device.

[0012] According to the present disclosure, it is possible to provide a communication system, a control device, a communication method, a control method, and a non-transitory computer-readable medium that are capable of performing encrypted communication without key relay.

[0013] FIG. 1 is a configuration diagram showing a configuration example of a related network system. FIG. 2 is a configuration diagram showing a configuration example of another related network system. FIG. 3 is a configuration diagram showing a configuration example of a network system according to an embodiment. FIG. 4 is a configuration diagram showing a configuration example of another network system according to an embodiment. FIG. 5 is a configuration diagram showing a configuration example of an optical network controller according to an embodiment. FIG. 6 is a configuration diagram showing a configuration example of an optical network system according to embodiment 1. FIG. 7 is a configuration diagram showing a configuration example of an optical network controller according to embodiment 1. FIG. 8 is a configuration diagram showing a configuration example of a transmitting end node according to embodiment 1. FIG. 9 is a configuration diagram showing a configuration example of a relay node according to embodiment 1. FIG. 10 is a configuration diagram showing a configuration example of a receiving end node according to embodiment 1. FIG. 11 is a sequence diagram showing an operation example of an optical network system according to embodiment 1. FIG. 12 is a flowchart showing an operation example of a path setting process according to embodiment 1. FIG. 13 is a configuration diagram showing an overview of hardware of a computer according to an embodiment.

[0014] Hereinafter, embodiments will be described with reference to the drawings. In each drawing, the same elements are given the same reference numerals, and duplicate explanations will be omitted as necessary. Note that the arrows shown in each drawing are examples for explanation purposes and do not limit the type or direction of signals.

[0015] (Discussion leading to the embodiment) Quantum key distribution is known as a technology that enables secure key sharing between two distant points by transmitting a random number sequence that is the source of a cryptographic key using a single photon. The use of a single photon can quantum-mechanically guarantee that the cryptographic key will not be leaked, thereby achieving high confidentiality, and it is expected to be used in cryptographic communications that handle important confidential information.

[0016] Single-photon detection is a method for detecting weak light such as a single photon. Single-photon detection measures a discrete physical quantity, the number of photons, and in most cases determines whether one or more photons have arrived. Quantum key distribution methods that use single-photon detection are called discrete variable quantum key distribution (DV-QKD), and research and development of the BB84 protocol is currently underway as the method closest to practical application.

[0017] In DV-QKD, when weak signal light and normal signal light are wavelength-multiplexed and transmitted, the normal signal light has a large effect on the weak signal light, making quantum key generation extremely difficult. For this reason, it is necessary to build a dedicated optical fiber network for quantum key distribution, which must be separated from the optical fiber network that carries normal optical signals.

[0018] Furthermore, in quantum key distribution, there is a limit to the distance between two points that share a quantum key, so key relay is necessary.

[0019] 1 shows an example of the configuration of a related network system, which is a network system 900 that distributes keys using DV-QKD. In the example of Fig. 1, nodes 910a to 910d are placed at points A to D, respectively, and end-to-end encrypted communication is performed from point A to point D.

[0020] 1, each node 910 is connected by an optical fiber 931 for quantum key distribution, and further by an optical fiber 932 for key relay. Point A and point B are connected by an arbitrary network such as the Internet for encrypted communication.

[0021] Each node 910 performs quantum key distribution using DV-QKD with a QKD transmitter (QTx) 911 and a QKD receiver (QRx) 912, and performs key relay with an encoder (Enc) 913, which is an encryption device, and a decoder (Dec) 914, which is a decryption device. Also, an encoder (Enc) 915 that encrypts transmission data using an encryption key is located at point A, and a decoder (Dec) 916 that decrypts received data using the encryption key is located at point D.

[0022] In the example of FIG. 1 , key relaying is performed as follows (S1) to (S4). (S1) A quantum key K1 is shared between point A and point B by a QKD transmitter 911a and a QKD receiver 912a, a quantum key K2 is shared between point B and point C by a QKD transmitter 911b and a QKD receiver 912b, and a quantum key K3 is shared between point C and point D by a QKD transmitter 911c and a QKD receiver 912c. (S2) At point B, an encoder 913b encrypts the key K1 to be relayed using key K2 and sends the encrypted key K1 from point B to point C. At point C, a decoder 914b decrypts the received data using key K2 to obtain key K1. At this time, key K1 is securely relayed from point B to point C by using one-time-pad as the encryption method. One-time-pad is an encryption method that uses a key of the same length as the data, and its impossibility of decryption has been mathematically proven. (S3) At point C, encoder 913c encrypts key K1 to be relayed using key K3 and sends the encrypted key K1 from point C to point D. At point D, decoder 914c decrypts the received data using key K3 to obtain key K1. As in (S2), by using one-time-pad as an encryption method, key K1 is securely relayed from point C to point D. (S4) As a result, points A and D can share encryption key K1. Encoder 915 at point A encrypts the data to be transmitted using key K1 and transmits the encrypted data via an arbitrary network. Decoder 916 at point D decrypts the received data using key K1 and obtains the decrypted data.

[0023] As mentioned above, the optical fiber for quantum key distribution must be separated from other optical fiber networks, and therefore must also be separated from the communication path for key relay. That is, as shown in Figure 1, two optical fibers are required between two points for quantum key distribution: an optical fiber 931 for quantum key distribution and an optical fiber 932 for key relay. In addition, a path for encrypted communication of data between points A and D is also required, and encrypted communication using a quantum encryption key requires a three-layer structure consisting of a quantum key distribution layer, a key relay layer, and an encrypted communication layer.

[0024] 1 , a key relay controller 920 is required to control the key relay of each node 910 in order to perform key relay from point A to point D. The key relay controller 920 controls the route for key relay between node 910a at point A and node 910d at point D. The key relay controller 920 manages the amount of keys generated by quantum key distribution at each node 910, and determines the node 910 that will perform key relay from point A to point D according to the amount of keys generated at each node 910, and controls the relay operation of each node 910.

[0025] Meanwhile, another promising method for detecting weak light is coherent detection. Coherent detection measures a continuous physical quantity, the quadrature amplitude of an electric field. Quantum key distribution using coherent detection is called continuous variable quantum key distribution (CV-QKD), and while research into this method is relatively new compared to DV-QKD, in recent years unconditional security has been theoretically demonstrated, and research is progressing, with implementation experiments also progressing.

[0026] Fig. 2 shows a configuration example of a network system 800 that performs key distribution using CV-QKD, which is another related network system. Fig. 2 shows an example in which CV-QKD is applied to the network system 900 of Fig. 1. In the example of Fig. 2, each node 910 performs quantum key distribution using CV-QKD using a QKD transmitter 917 and a QKD receiver 918.

[0027] CV-QKD, thanks to the filtering function of coherent detection, can generate quantum keys even when weak optical signals and ordinary optical signals are wavelength-multiplexed. While DV-QKD requires two optical fibers for the quantum key distribution layer and the key relay layer, CV-QKD enables wavelength-multiplexed transmission of these two layers. Furthermore, CV-QKD enables quantum key generation in the associated optical fiber network that performs wavelength-multiplexed transmission, allowing the quantum key distribution layer and the key relay layer to be established within the associated optical fiber network. That is, as shown in Figure 2, the optical fiber 930 connecting each node 910 can multiplex key distribution links QL1 to QL3 that perform key distribution and encryption links L1 to L3 that perform key relay.

[0028] As a result of the inventor's investigation into the example shown in Fig. 2, the following problem was discovered. In the related optical fiber network that performs wavelength division multiplexing transmission, an optical network controller is used to control wavelengths, bandwidths, and routes, and it is conceivable to provide an optical network controller 940 that controls each node 910, as shown in Fig. 2. However, the related optical network controller 940 does not have the concept of managing quantum keys. Therefore, in order to perform key relay within the related optical network as shown in Fig. 2, the concept of key relay must be added to the optical network controller 940, which is a problem.

[0029] Furthermore, as shown in Figure 2, there is also the problem that the quantum key-based encrypted communication layer is separated from other layers, and no specific method has been established for providing an encrypted communication layer within an optical network.

[0030] (Outline of the embodiment) An outline of the embodiment will now be described. Fig. 3 shows an example of the configuration of a network system according to the embodiment.

[0031] As shown in FIG. 3 , a network system (communication system) 1 according to an embodiment includes nodes 10a to 10d arranged at points A to D, respectively, and an optical network controller 20. The number of nodes 10 is not limited to four and may be any number, for example, three or more. Each node 10 is a communication device that includes, for example, a trusted node (QKD node), shares a quantum key by performing quantum key distribution using CV-QKD, and performs encrypted communication using the shared key. The nodes 10 are connected to each other by optical fiber 30. For example, in the optical fiber 30, signals of key distribution links QL1 to QL3 that perform key distribution between the nodes and signals of encryption links L1 to L3 that perform encrypted communication between the nodes are wavelength-multiplexed.

[0032] In this example, similar to FIGS. 1 and 2, the node 10a at point A is the transmitting end node, the nodes 10b and 10c at points B and C are relay nodes, and the node 10d at point D is the receiving end node.

[0033] The node 10a includes a QKD transmitter 11a and an encoder 13a. The QKD transmitter 11a is a key distribution unit that shares a key K1 with the node 10b (QKD receiver 12a) by performing key distribution using CV-QKD via a key distribution link QL1. The encoder 13a is an encryption unit that encrypts input transmission data, i.e., data to be transmitted to the node 10b, using the key K1 shared with the node 10b. The encoder 13a transmits the encrypted data to the node 10b via the encryption link L1.

[0034] The node 10b includes a QKD receiver 12a, a decoder 14a, a QKD transmitter 11b, and an encoder 13b. The QKD receiver 12a is a key distribution unit that shares a key K1 with the node 10a (QKD transmitter 11a) by performing key distribution using CV-QKD via a key distribution link QL1. The decoder 14a is a decryption unit that decrypts data received via an encrypted link L1 using the key K1. The QKD transmitter 11b is a key distribution unit that shares a key K2 with the node 10c (QKD receiver 12b) by performing key distribution using CV-QKD via a key distribution link QL2. The encoder 13b is an encryption unit that encrypts the data decrypted by the decoder 14a, i.e., the data to be transmitted to the node 10c, using the key K2 shared with the node 10c. The encoder 13b transmits the encrypted data to the node 10c via an encrypted link L2.

[0035] The node 10c includes a QKD receiver 12b, a decoder 14b, a QKD transmitter 11c, and an encoder 13c. The QKD receiver 12b is a key distribution unit that shares a key K2 with the node 10b (QKD transmitter 11b) by performing key distribution using CV-QKD via a key distribution link QL2. The decoder 14b is a decryption unit that decrypts data received via an encrypted link L2 using the key K2. The QKD transmitter 11c is a key distribution unit that shares a key K3 with the node 10d (QKD receiver 12c) by performing key distribution using CV-QKD via a key distribution link QL3. The encoder 13c is an encryption unit that encrypts the data decrypted by the decoder 14b, i.e., the data to be transmitted to the node 10d, using the key K3 shared with the node 10d. The encoder 13c transmits the encrypted data to the node 10d via an encrypted link L3.

[0036] The node 10d includes a QKD receiver 12c and a decoder 14c. The QKD receiver 12c is a key distribution unit that shares a key K3 with the node 10c (QKD transmitter 11c) by performing key distribution using CV-QKD via a key distribution link QL3. The decoder 14c is a decryption unit that decrypts data received via the encrypted link L3 using the key K3. The decoder 14c outputs the decrypted data as received data.

[0037] The optical network controller 20 is a control device that controls communications between the nodes 10a to 10d. In order for the nodes 10a and 10d to perform encrypted communications, the optical network controller 20 connects encrypted links L1, L2, and L3 to establish an encrypted communication path from the node 10a to the node 10d. The optical network controller 20 controls the nodes 10a to 10d so that encrypted communications are performed over the established encrypted communication path. For example, the optical network controller 20 defines an encrypted link L1 that performs encrypted communications using a quantum key K1, an encrypted link L2 that performs encrypted communications using a quantum key K2, and an encrypted link L3 that performs encrypted communications using a quantum key K3, and sets up a path via the defined encrypted links L1, L2, and L3.

[0038] The network system 1 according to the embodiment may have at least the configuration shown in Fig. 4. For example, as shown in Fig. 4, the network system 1 may include nodes 10a to 10c and an optical network controller 20.

[0039] The node 10a (first communication device) may include an encoder (first encryption unit) that encrypts data to be transmitted to the node 10b using a key K1 (first key) shared with the node 10b. The node 10b (second communication device) may include a decoder (first decryption unit) that decrypts data received from the node 10a using the key K1, and an encoder (second encryption unit) that encrypts data to be transmitted to the node 10c using a key K2 (second key) shared with the node 10c. The node 10c (third communication device) may include a decoder (second decryption unit) that decrypts data received from the node 10b using the key K2.

[0040] The optical network controller 20 (control device) may include a setting unit 21 that connects an encrypted link L1 (first encrypted link) between the encoder 13a and the decoder 14a and an encrypted link L2 (second encrypted link) between the encoder 13b and the decoder 14c to set up an encrypted communication path from the node 10a to the node 10c.

[0041] The optical network controller 20 shown in the example of Fig. 4 may also be configured as shown in Fig. 5. As shown in Fig. 5, for example, the optical network controller 20 may include a setting unit 21 and an acquiring unit 22. The acquiring unit 22 may acquire information about the link connecting the node 10a and the node 10b, and information about the link connecting the node 10b and the node 10c. For example, the information about the link is information indicating whether the link is an encrypted link. Based on the information acquired by the acquiring unit 22, the setting unit 21 may connect the encrypted link L1 and the encrypted link L2 to set an encrypted communication path from the node 10a to the node 10c.

[0042] As described above, in the embodiment, encryption keys are shared between each node, and encrypted links between nodes that perform encrypted communication using the shared key are connected to establish an encrypted communication path for end-to-end encrypted communication. This enables encrypted communication without key relay. Furthermore, there is no need to provide a key relay controller, and there is no need to add functions to the optical network controller for key management and key relay control. Furthermore, the key relay layer is no longer necessary, and the encrypted communication layer and quantum key distribution layer can be multiplexed and integrated into the optical network.

[0043] (First Embodiment) Next, a first embodiment will be described. Fig. 6 shows an example of the configuration of an optical network system according to this embodiment. As shown in Fig. 6, an optical network system 2 according to this embodiment includes a transmitting end node 100, a plurality of relay nodes 200, a receiving end node 300, and an optical network controller 400. Note that any of the transmitting end node 100, the relay node 200, and the receiving end node 300 may be simply referred to as a node. Fig. 6 is an example, and any node may be the transmitting end node 100, the relay node 200, or the receiving end node 300.

[0044] The transmitting end node 100, the relay node 200, and the receiving end node 300 are connected to each other via optical fibers (optical transmission paths) 3 so as to be capable of optical communication. The transmitting end node 100, the relay node 200, and the receiving end node 300 are connected to the optical network controller 400 via any transmission path, including wired and wireless, so as to be capable of communicating control signals.

[0045] The transmitting end node 100 (first communication device), the relay node 200 (second communication device), and the receiving end node 300 (third communication device) are optical communication devices (optical nodes) that perform optical communication via optical fiber 3, and are also capable of performing quantum key distribution and encrypted communication via the optical fiber 3. The transmitting end node 100 and the receiving end node 300 are the transmitting end and receiving end nodes in the path. The relay node 200 is a node that performs relay processing between the transmitting end node 100 and the receiving end node 300 in the path.

[0046] The transmitting end node 100, the relay node 200, and the receiving end node 300 constitute an optical network 4. For example, the optical network 4 is a wavelength-multiplexed optical network, and the transmitting end node 100, the relay node 200, and the receiving end node 300 transmit and receive wavelength-multiplexed optical signals. The optical network 4 may be a mesh-shaped network, a ring-shaped network, a point-to-point network, or a network of other topologies, but optical amplifiers are not included in each node or in the links between nodes. Nodes including the transmitting end node 100, the relay node 200, and the receiving end node 300 are connected by key distribution links for key distribution and encrypted links for encrypted communication. Nodes may also be connected by links for normal communication (unencrypted links) that do not use encryption. A link is a logical connection unit for optical communication between nodes using optical signals of a predetermined wavelength, and multiple wavelengths (wavelength channels) may be used in one link. The encryption link may use wavelengths whose number corresponds to the amount of data to be transmitted, and the key distribution link may use wavelengths whose number corresponds to the amount of signal required for key distribution. The key distribution link (QKD link) may include a quantum channel for transmitting and receiving quantum signals, which are weak light for key distribution, and a classical channel for exchanging information for synchronization and key distillation.

[0047] The transmitting end node 100, the relay node 200, and the receiving end node 300 configure a path from the transmitting end node 100 to the receiving end node 300 in accordance with control from the optical network controller 400, and transmit an optical signal (data) at a wavelength set on the path route. For example, an encrypted communication path is configured from the transmitting end node 100 to the receiving end node 300, and encrypted communication is performed via the encrypted communication path, but a normal path (unencrypted communication path) that does not use encryption may also be configured.

[0048] The sending end node 100 transmits an optical signal obtained by wavelength-multiplexing an optical signal of an encryption link having a set wavelength and an optical signal of a key distribution link having a predetermined wavelength to the relay node 200 via the optical fiber 3. The relay node 200 receives the wavelength-multiplexed optical signal from the sending end node 100 or another relay node 200 via the optical fiber 3, and further transmits an optical signal obtained by wavelength-multiplexing an optical signal of an encryption link having a set wavelength and an optical signal of a key distribution link having a predetermined wavelength to another relay node 200 or the receiving end node 300 via the optical fiber 3. The receiving end node 300 receives the wavelength-multiplexed optical signal from the relay node 200 via the optical fiber 3.

[0049] The optical network controller 400 is a control device that manages and controls the optical network 4 including the transmitting end node 100, the relay node 200, and the receiving end node 300. For example, the optical network controller 400 may be an NMS (Network Management System) that manages the network.

[0050] The optical network controller 400 controls the operations of the transmitting end node 100, relay node 200, and receiving end node 300 that constitute the optical network 4. For example, the optical network controller 400 manages and controls the configurations and paths of the transmitting end node 100, relay node 200, and receiving end node 300. The optical network controller 400 sets the route and wavelength of the path from the transmitting end node 100 to the receiving end node 300, and notifies the transmitting end node 100, relay node 200, and receiving end node 300 on the path of the route, wavelength, etc. For example, the optical network controller 400 sets an encrypted communication path connecting encrypted links between the transmitting end node 100, relay node 200, and receiving end node 300.

[0051] 7 shows an example of the configuration of an optical network controller 400 according to this embodiment. As shown in FIG. 7, the optical network controller 400 includes a management unit 410 and a setting unit 420.

[0052] The management unit 410 manages information necessary for network control, such as network configuration information. For example, the management unit 410 may be configured as a database that stores information necessary for network control. The management unit 410 is also an acquisition unit that acquires information necessary for network control. The network configuration information includes information on the connection relationships of each node that constitutes the optical network 4 and information on the links connecting each node. The link information includes information that identifies whether or not the link is an encrypted link for performing encrypted communication. The network configuration information may include configuration information of each node, wavelengths, transmission bands, throughput, etc. that can be used by each node. This information may be set in a database in advance, or may be set from information collected from each node.

[0053] The setting unit 420 sets (controls) the transmitting end node 100, the relay node 200, and the receiving end node 300 based on information managed by the management unit 410. The setting unit 420 sets a path from the transmitting end node 100 to the receiving end node 300 based on information about the connection relationships and links between each node, and may determine the wavelengths to be used in the path depending on the wavelength usage status. For example, when setting an encrypted communication path, the setting unit 420 extracts encrypted links from the links connecting each node, and connects the extracted encrypted links to set the encrypted communication path. The setting unit 420 notifies each node of information necessary for encrypted communication over the set path. For example, the setting unit 420 may notify each node of wavelength information of the encrypted links transmitted and received by the node, or connection information for the encrypted links.

[0054] Fig. 8 shows an example of the configuration of a transmitting end node 100 according to this embodiment. As shown in Fig. 8, the transmitting end node 100 includes a trusted node 110, a multiplexer 120, and a node control unit 130. Note that the transmitting end node 100 may also include an optical transmitter for normal communication that does not use encryption.

[0055] The trusted node 110 includes a QKD transmitter 111, an encoder 112, and an optical transmitter 113. The trusted node 110 can be configured from multiple devices, and the security of input and output of signals (including keys) between devices within the trusted node 110 is guaranteed.

[0056] The QKD transmitter 111 (first key distribution unit) is a transmitter that performs quantum key distribution via a key distribution link QL1. The QKD transmitter 111 generates (shares) a quantum key K1 by performing key distribution with a QKD receiver (e.g., a QKD receiver at an intermediate node) connected via an optical fiber 3a. The QKD transmitter 111 outputs the generated quantum key (also referred to as an encryption key or simply as a key) K1 to the encoder 112.

[0057] The QKD transmitter 111 performs key distribution using CV-QKD. The QKD transmitter 111 can be implemented with a configuration similar to that of an optical transmitter used in coherent communications. For example, the QKD transmitter 111 includes an MZ modulator (IQ optical modulator) that applies IQ modulation to light from a light source and an attenuator that attenuates the intensity of the IQ-modulated optical signal. The attenuator outputs the attenuated optical signal as a quantum signal, which is weak light. For example, the wavelength of the key distribution link QL1 is set in advance, and the QKD transmitter 111 transmits a quantum signal of a predetermined wavelength as an optical signal for the key distribution link QL1. The QKD transmitter 111 may also include a key distillation unit that generates (shares) a secure key based on the quantum signal received by the QKD receiver through key distillation processing.

[0058] The encoder 112 (first encryption unit) encrypts input data using the key K1 generated by the QKD transmitter 111. Transmission data to be transmitted by encrypted communication from the transmitting end node 100 to the receiving end node 300 is input to the encoder 112. The encryption method may be one-time-pad or another method. The encoder 112 outputs the encrypted data to the optical transmitter 113.

[0059] The optical transmitter 113 generates an optical signal for optical transmission from the encrypted data encrypted by the encoder 112 and transmits the generated optical signal as a signal of the encrypted link L1. The optical transmitter 113 may generate an optical signal by modulating the encrypted data using a modulation method for coherent communication or any other modulation method. The optical transmitter 113 generates an optical signal with a wavelength set by the node control unit 130 as the wavelength of the encrypted link L1.

[0060] The multiplexer 120 (first multiplexing unit) multiplexes optical signals of multiple wavelengths into one optical signal (wavelength multiplexing) and transmits the multiplexed optical signal (first multiplexed signal) to the optical fiber 3a (first optical fiber). The multiplexer 120 wavelength-multiplexes the optical signal (quantum signal) of the key distribution link QL1 output from the QKD transmitter 111 and the optical signal of the encrypted link L1 output from the optical transmitter 113. Note that the multiplexer 120 may further wavelength-multiplex an optical signal of a link for normal communication that is not encrypted, i.e., an optical signal transmitted by an optical transmitter for normal communication.

[0061] The node control unit 130 controls the operation of the trusted node 110 in accordance with settings from the optical network controller 400. The node control unit 130 acquires wavelength information of the encrypted link L1 from the optical network controller 400, and sets the wavelength of the optical signal of the encrypted link L1 transmitted by the optical transmitter 113 based on the acquired wavelength information. Note that the node control unit 130 may also set the wavelength of the key distribution link QL1 used by the QKD transmitter 111 in accordance with settings from the optical network controller 400. Furthermore, the node control unit 130 may set the wavelength of the optical signal of a link for normal communication that is not encrypted, i.e., the wavelength used by an optical transmitter for normal communication.

[0062] Fig. 9 shows an example of the configuration of a relay node 200 according to this embodiment. As shown in Fig. 9, the relay node 200 includes a trusted node 210, a demultiplexer 220, and a multiplexer 230. Note that the relay node 200 may also include an optical receiver and an optical transmitter for normal communication that does not use encryption.

[0063] The demultiplexer 220 (first demultiplexing unit) demultiplexes the optical signal (first multiplexed signal) received from the optical fiber 3a into optical signals of multiple wavelengths. The demultiplexer 220 demultiplexes the received optical signal into an optical signal for the key distribution link QL1 and an optical signal for the encryption link L1 according to the wavelength. Note that the demultiplexer 220 may further demultiplex an optical signal for a link for normal communication that is not encrypted, i.e., an optical signal received by an optical receiver for normal communication, from the received optical signal.

[0064] The trusted node 210 includes a QKD receiver 211, an optical receiver 212, a decoder 213, a QKD transmitter 214, an encoder 215, and an optical transmitter 216. The trusted node 210 can be configured from multiple devices, similar to the trusted node 110 of the sending end node 100, and the security of signal input and output between devices within the trusted node 210 is guaranteed.

[0065] The QKD receiver 211 (second key distribution unit) is a receiver that performs quantum key distribution via a key distribution link QL1. The QKD receiver 211 generates (shares) a quantum key K1 by performing key distribution with a QKD transmitter (e.g., a QKD transmitter of a transmitting end node or a relay node) connected via an optical fiber 3a. The QKD receiver 211 outputs the generated quantum key K1 to the decoder 213.

[0066] The QKD receiver 211 performs key distribution using CV-QKD. The QKD receiver 211 can be implemented with a configuration similar to that of an optical receiver used in coherent communications. For example, the QKD receiver 211 includes a coherent detector such as a 90-degree hybrid circuit. The coherent detector performs coherent detection by causing interference between a received optical signal (quantum signal) and local light to generate an IQ signal. For example, the wavelength of the key distribution link QL1 is set in advance, and the QKD receiver 211 receives an optical signal of a predetermined wavelength from the optical signals separated by the demultiplexer 220 as a quantum signal of the QKD link. The QKD receiver 211 may also include a key distillation unit that generates (shares) a secure key based on the quantum signal received from the QKD transmitter using a key distillation process.

[0067] The optical receiver 212 receives an optical signal for optical transmission via the encrypted link L1 and generates (demodulates) encrypted data from the received optical signal. The optical receiver 212 may demodulate the optical signal into encrypted data according to a modulation method for coherent communication or any other modulation method. The optical receiver 212 receives, as the signal of the encrypted link L1, an optical signal having a wavelength set by the node control unit 240 as the wavelength of the encrypted link L1 from among the optical signals separated by the demultiplexer 220. The optical receiver 212 outputs the received and demodulated encrypted data to the decoder 213.

[0068] The decoder 213 (first decryption unit) decrypts the encrypted data received by the optical receiver 212 using the key K1 generated by the QKD receiver 211. The encryption method may be one-time-pad or another method. The decoder 213 outputs the decrypted data to the encoder 215. The decoder 213 may output the decrypted data to the encoder 215 in accordance with an instruction from the node control unit 240 to connect the encrypted link L1 and the encrypted link L2. That is, the decoder 213 transfers the data received from the encrypted link L1 to the encrypted link L2 via the encoder 215.

[0069] The QKD transmitter 214, encoder 215, and optical transmitter 216 are similar to the QKD transmitter 111, encoder 112, and optical transmitter 113 of the sending end node 100. That is, the QKD transmitter 214 (third key distribution unit) generates a quantum key K2 by performing key distribution with a QKD receiver (e.g., a QKD receiver of an intermediate node or a receiving end node) via a key distribution link QL2. The encoder 215 (second encryption unit) encrypts the data decrypted by the decoder 213 using the key K2 generated by the QKD transmitter 214. The optical transmitter 216 generates an optical signal for optical transmission from the encrypted data encrypted by the encoder 215 and transmits the generated optical signal as a signal of the encrypted link L2.

[0070] Similar to the multiplexer 120 of the sending end node 100, the multiplexer 230 (second multiplexing unit) wavelength-multiplexes the optical signal of the key distribution link QL2 output from the QKD transmitter 214 and the optical signal of the encrypted link L2 output from the optical transmitter 216, and transmits the wavelength-multiplexed optical signal (second multiplexed signal) to the optical fiber 3b (second optical fiber). Note that the multiplexer 120 may further wavelength-multiplex an optical signal of a link for normal communication that is not encrypted, i.e., an optical signal transmitted by an optical transmitter for normal communication.

[0071] The node control unit 240 controls the operation of the trusted node 210 in accordance with settings from the optical network controller 400. The node control unit 240 acquires wavelength information of the encrypted links L1 and L2 from the optical network controller 400, and based on the acquired wavelength information, sets the wavelength of the optical signal of the encrypted link L1 received by the optical receiver 212 and sets the wavelength of the optical signal of the encrypted link L2 transmitted by the optical transmitter 216. The node control unit 240 also acquires connection information of the encrypted links L1 and L2 from the optical network controller 400, and based on the acquired connection information, instructs the decoder 213 to connect the encrypted links L1 and L2. The node control unit 240 may also instruct the encoder 215 to connect the encrypted links L1 and L2. The node control unit 240 may also set the wavelength of the key distribution link QL1 used by the QKD receiver 211 and the wavelength of the key distribution link QL2 used by the QKD transmitter 214 in accordance with settings from the optical network controller 400. Furthermore, the node control unit 240 may set the wavelength of the optical signal of the link for normal communication that is not encrypted, that is, the wavelength used by the optical receiver and optical transmitter for normal communication.

[0072] Fig. 10 shows an example of the configuration of a receiving end node 300 according to this embodiment. As shown in Fig. 10, the receiving end node 300 includes a trusted node 310, a demultiplexer 320, and a node control unit 330. Note that the receiving end node 300 may also include an optical receiver for normal communication that does not use encryption.

[0073] The demultiplexer 320 (second separation unit) separates the optical signal (second multiplexed signal) received from the optical fiber 3b into an optical signal of the key distribution link QL2 and an optical signal of the wavelength of the encryption link L2, similar to the demultiplexer 220 of the relay node 200. Note that the demultiplexer 320 may further separate, from the received optical signal, an optical signal of a link for normal communication that is not encrypted, i.e., an optical signal received by an optical receiver for normal communication.

[0074] The trusted node 310 includes a QKD receiver 311, an optical receiver 312, and a decoder 313. Like the trusted node 110 of the sending end node 100, the trusted node 310 can be configured from multiple devices, and the security of signal input and output between devices within the trusted node 310 is guaranteed.

[0075] The QKD receiver 311, optical receiver 312, and decoder 313 are similar to the QKD receiver 211, optical receiver 212, and decoder 213 of the relay node 200. That is, the QKD receiver 311 (fourth key distribution unit) generates a quantum key K2 by performing key distribution with a QKD transmitter (e.g., a QKD transmitter of a relay node) via a key distribution link QL2. The optical receiver 312 generates encrypted data from an optical signal received via the encryption link L2. The decoder 313 (second decryption unit) decrypts the encrypted data received by the optical receiver 312 using the key K2 generated by the QKD receiver 311. The decoder 313 outputs the decrypted data. The output data is the data input to and transmitted from the transmitting end node 100.

[0076] The node control unit 330 controls the operation of the trusted node 310 in accordance with settings from the optical network controller 400. The node control unit 330 acquires wavelength information of the encrypted link L2 from the optical network controller 400, and sets the wavelength of the optical signal of the encrypted link L2 received by the optical receiver 312 based on the acquired wavelength information. Note that the node control unit 330 may also set the wavelength of the key distribution link QL2 used by the QKD receiver 311 in accordance with settings from the optical network controller 400. Furthermore, the node control unit 330 may set the wavelength of the optical signal of a link for normal communication that is not encrypted, i.e., the wavelength used by an optical receiver for normal communication.

[0077] 11 shows an example of the operation of the optical network system according to this embodiment. As an example, FIG. 11 shows an example in which one relay node 200 relays encrypted communications. As shown in FIG. 11 , the transmitting end node 100, the relay node 200, and the receiving end node 300 perform key distribution between each node (S101). Key distribution is performed between the QKD transmitter 111 of the transmitting end node 100 and the QKD receiver 211 of the relay node 200 via a key distribution link QL1, and a quantum key K1 is shared. Furthermore, key distribution is performed between the QKD transmitter 214 of the relay node 200 and the QKD receiver 311 of the receiving end node 300 via a key distribution link QL2, and a quantum key K2 is shared. Key distribution is continuously performed between each node, and quantum keys K1 and K2 are repeatedly generated.

[0078] Next, the optical network controller 400 sets up a path from the transmitting end node 100 to the receiving end node 300 (S102).

[0079] 12 shows an example of the operation of the path setting process in S102. As shown in Fig. 12, the setting unit 420 of the optical network controller 400 identifies the transmitting end node 100 and the receiving end node 300 (S201). The setting unit 420 identifies the transmitting end node 100 and the receiving end node 300 that will perform encrypted communication from among the nodes in the optical network 4. For example, information for identifying the nodes may be input from the outside, and the transmitting end node 100 and the receiving end node 300 may be identified according to the input information, or the transmitting end node 100 and the receiving end node 300 may be identified according to preset information.

[0080] Next, the setting unit 420 selects a route between the identified transmitting end node 100 and receiving end node 300 (S202). The setting unit 420 selects a route from the transmitting end node 100 to the receiving end node 300 based on information on the connection relationships between nodes managed by the management unit 410. The setting unit 420 may select a route to be used for a path based on available wavelengths, transmission bands, throughput, etc.

[0081] Next, the setting unit 420 extracts encrypted links from the selected route (S203). Based on information about links between nodes managed by the management unit 410, the setting unit 420 extracts encrypted links from the links between nodes included in the selected route. The setting unit 420 determines whether there is an encrypted link from the sending end node 100 to the receiving end node 300, and may select a new route if there is no encrypted link from the sending end node 100 to the receiving end node 300. For example, the setting unit 420 extracts the encrypted link L1 between the sending end node 100 and the relay node 200 and the encrypted link L2 between the relay node 200 and the receiving end node 300.

[0082] Next, the setting unit 420 connects the extracted encrypted links and sets up an encrypted communication path from the sending end node 100 to the receiving end node 300 (S204). For example, the setting unit 420 connects the encrypted link L1 and the encrypted link L2 to set up an encrypted communication path. The setting unit 420 determines the wavelengths of the encrypted links L1 and L2 that make up the encrypted communication path, and notifies the sending end node 100, the relay node 200, and the receiving end node 300 of the wavelength information of the encrypted links L1 and L2. The setting unit 420 also notifies the relay node 200 of connection information indicating the connection between the encrypted link L1 and the encrypted link L2.

[0083] Then, the node control unit 130 of the sending end node 100 sets the wavelength of the optical signal of the encrypted link L1 to be transmitted by the optical transmitter 113 based on the notified wavelength information. The node control unit 240 of the intermediate node 200 sets the wavelength of the optical signal of the encrypted link L1 to be received by the optical receiver 212 based on the notified wavelength information, and sets the wavelength of the optical signal of the encrypted link L2 to be transmitted by the optical transmitter 216 based on the notified wavelength information. Furthermore, the node control unit 240 of the intermediate node 200 instructs the decoder 213 to connect the encrypted links L1 and L2 based on the notified connection information. The node control unit 330 of the receiving end node 300 sets the wavelength of the optical signal of the encrypted link L2 to be received by the optical receiver 312 based on the notified wavelength information.

[0084] 11, the transmitting end node 100 encrypts the data to be transmitted (S103). The encoder 112 encrypts the input transmission data using the encryption key K1 generated by the QKD transmitter 111.

[0085] Next, the sending end node 100 transmits the encrypted data to the relay node 200 (S104). The optical transmitter 113 modulates the encrypted data encrypted by the encoder 112 into an optical signal with a wavelength set by the node control unit 130, and transmits the modulated data as an optical signal of the encrypted link L1 to the optical fiber 3a via the multiplexer 120.

[0086] Next, the relay node 200 receives the encrypted data from the sending end node 100 (S105). The optical receiver 212 receives an optical signal having the wavelength of the encrypted link L1 set by the node control unit 240 from the optical fiber 3a via the demultiplexer 220, and demodulates the encrypted data from the received optical signal.

[0087] Next, the relay node 200 decrypts the received encrypted data (S106). The decoder 213 decrypts the encrypted data received by the optical receiver 212 using the encryption key K1 generated by the QKD receiver 211. The decoder 213 outputs the decrypted data to the encoder 215 in accordance with an instruction from the node control unit 240 to connect the encrypted link L1 and the encrypted link L2.

[0088] Next, the relay node 200 encrypts the decrypted data (S107). The encoder 215 encrypts the data decrypted by the decoder 213 using the encryption key K2 generated by the QKD transmitter 214.

[0089] Next, the relay node 200 transmits the encrypted data to the receiving end node 300 (S108). The optical transmitter 216 modulates the encrypted data encrypted by the encoder 215 into an optical signal with a wavelength set by the node control unit 240, and transmits the modulated data as an optical signal of the encrypted link L2 to the optical fiber 3b via the multiplexer 230.

[0090] Next, the receiving end node 300 receives the optical signal containing the encrypted data from the relay node 200 (S109). The optical receiver 312 receives the optical signal having the wavelength of the encrypted link L2 set by the node control unit 330 from the optical fiber 3b via the demultiplexer 320, and demodulates the encrypted data from the received optical signal.

[0091] Next, the receiving end node 300 decrypts the received encrypted data (S110). The decoder 313 decrypts the encrypted data received by the optical receiver 312 using the encryption key K2 generated by the QKD receiver 311. The decoder 313 outputs the decrypted data.

[0092] As described above, in this embodiment, the optical network controller manages encrypted links using quantum keys between each node and connects the encrypted links to set up a path from the transmitting end node to the receiving end node. Data to be encrypted is input to the transmitting end node, and each node directly encrypts the data with a quantum key and forwards the data to the receiving end node via the encrypted link. This enables encrypted communication from the transmitting end node to the receiving end node without key relay. The optical relay controller enables encrypted communication simply by setting up a path, without the need for key management or key relay control. Furthermore, by wavelength-multiplexing the signals of the quantum key distribution layer and the encrypted communication layer, quantum key distribution and encrypted communication using quantum keys can be performed within the same optical network.

[0093] The present disclosure is not limited to the above-described embodiments, and modifications can be made as appropriate without departing from the spirit of the present disclosure. For example, in the above-described embodiments, an example of wavelength multiplexing has been described as a multiplexing method in an optical network, but multiplexing is not limited to wavelength multiplexing, and polarization multiplexing or other methods may also be used. Furthermore, in the above-described embodiments, an example of quantum key distribution using CV-QKD has been described, but quantum key distribution may be performed using other methods as long as multiplexing of key distribution links and encryption links is possible.

[0094] Each component in the above-described embodiments may be configured with hardware or software, or both, and may be configured with a single piece of hardware or software, or may be configured with multiple pieces of hardware or software. Each device (optical network controller, etc.) and each function (processing) may be realized by a computer 40 having a processor 41 such as a CPU (Central Processing Unit) and a memory 42 serving as a storage device, as shown in FIG. 13. For example, a program for performing a method (control method, etc.) in the embodiment may be stored in the memory 42, and each function may be realized by having the processor 41 execute the program stored in the memory 42.

[0095] These programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0096] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure.

[0097] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes. (Supplementary Note 1) A communication system comprising: first, second, and third communication devices; and a control device that controls the first, second, and third communication devices; wherein the first communication device comprises first encryption means that encrypts data to be transmitted to the second communication device using a first key shared with the second communication device; the second communication device comprises first decryption means that decrypts data received from the first communication device using the first key; and second encryption means that encrypts data to be transmitted to the third communication device using a second key shared with the third communication device; the third communication device comprises second decryption means that decrypts data received from the second communication device using the second key; and the control device comprises setting means that connects a first encryption link between the first encryption means and the first decryption means and a second encryption link between the second encryption means and the second decryption means to set an encrypted communication path from the first communication device to the third communication device. (Supplementary Note 2) The communication system according to Supplementary Note 1, wherein the first communication device comprises first key distribution means for sharing the first key with the second communication device by performing quantum key distribution with the first communication device via the first key distribution link; the second communication device comprises second key distribution means for sharing the first key with the first communication device by performing the quantum key distribution with the first communication device via the first key distribution link; and third key distribution means for sharing the second key with the third communication device by performing the quantum key distribution with the third communication device via the second key distribution link; and the third communication device comprises fourth key distribution means for sharing the second key with the second communication device by performing the quantum key distribution with the second communication device via the second key distribution link.(Supplementary Note 3) The communication system according to Supplementary Note 2, wherein the first communication device comprises a first multiplexing means for multiplexing a signal of the first encrypted link and a signal of the first key distribution link and transmitting the multiplexed multiplexed signal; the second communication device comprises a first demultiplexing means for demultiplexing a multiplexed signal received from the first communication device into a signal of the first encrypted link and a signal of the first key distribution link, and a second multiplexing means for multiplexing a signal of the second encrypted link and a signal of the second key distribution link and transmitting the multiplexed multiplexed signal; and the third communication device comprises a second demultiplexing means for demultiplexing a multiplexed signal received from the second communication device into a signal of the second encrypted link and a signal of the second key distribution link. (Supplementary Note 4) The communication system according to Supplementary Note 3, wherein the first multiplexing means wavelength-multiplexes the signals of the first encrypted link and the signals of the first key distribution link, and the second multiplexing means wavelength-multiplexes the signals of the second encrypted link and the signals of the second key distribution link. (Supplementary Note 5) The communication system according to Supplementary Note 4, wherein the setting means sets wavelengths of the signals of the first encrypted link and the signals of the second encrypted link. (Supplementary Note 6) The communication system according to any one of Supplements 1 to 5, wherein the setting means extracts the first encrypted link capable of encrypted communication from information about a link connecting the first communication device and the second communication device, extracts the second encrypted link capable of encrypted communication from information about a link connecting the second communication device and the third communication device, and combines the extracted first encrypted link and second encrypted link.(Supplementary Note 7) A control device that controls first, second, and third communication devices, comprising: an acquisition means for acquiring information about a link connecting the first communication device and the second communication device and information about a link connecting the second communication device and the third communication device; and a setting means for setting an encrypted communication path from the first communication device to the third communication device by combining, based on the acquired information, a first encrypted link for performing encrypted communication between the first communication device and the second communication device using a first key and a second encrypted link for performing encrypted communication between the second communication device and the third communication device using a second key. (Supplementary Note 8) The control device according to Supplementary Note 7, wherein the first key is a key shared by performing quantum key distribution between the first communication device and the second communication device via a first key distribution link, and the second key is a key shared by performing quantum key distribution between the second communication device and the third communication device via a second key distribution link. (Supplementary Note 9) The control device according to Supplementary Note 8, wherein the setting means sets a wavelength of a signal of the first encrypted link to be wavelength-multiplexed with a signal of the first key distribution link, and sets a wavelength of a signal of the second encrypted link to be wavelength-multiplexed with a signal of the second key distribution link.(Supplementary Note 10) A communication method in a communication system including first, second, and third communication devices and a control device that controls the first, second, and third communication devices, wherein the first communication device encrypts data to be transmitted to the second communication device using a first key shared with the second communication device, the second communication device decrypts data received from the first communication device using the first key, and encrypts data to be transmitted to the third communication device using a second key shared with the third communication device, and the third communication device decrypts data received from the second communication device using the second key, and the control device connects a first encryption link between the first communication device and the second communication device using the first key and a second encryption link between the second communication device and the third communication device using the second key, thereby setting up an encrypted communication path from the first communication device to the third communication device. (Supplementary Note 11) The communication method according to Supplementary Note 10, wherein the first communication device shares the first key with the second communication device by performing quantum key distribution with the first communication device via a first key distribution link; the second communication device shares the first key with the first communication device by performing the quantum key distribution with the first communication device via the first key distribution link; the second communication device shares the second key with the third communication device by performing the quantum key distribution with the third communication device via a second key distribution link; and the third communication device shares the second key with the second communication device by performing the quantum key distribution with the second communication device via the second key distribution link. (Supplementary Note 12) A control method for controlling first, second, and third communication devices, comprising: acquiring information regarding a link connecting the first communication device and the second communication device, and information regarding a link connecting the second communication device and the third communication device; and based on the acquired information, combining a first encrypted link for performing encrypted communication between the first communication device and the second communication device using a first key, and a second encrypted link for performing encrypted communication between the second communication device and the third communication device using a second key, thereby setting up an encrypted communication path from the first communication device to the third communication device.(Supplementary Note 13) The control method according to Supplementary Note 12, wherein the first key is a key shared between the first communication device and the second communication device by performing quantum key distribution via a first key distribution link, and the second key is a key shared between the second communication device and the third communication device by performing quantum key distribution via a second key distribution link. (Supplementary Note 14) A non-transitory computer-readable medium storing a control program for causing a computer to execute a process of controlling first, second, and third communication devices, the control program comprising: acquiring information about a link connecting the first communication device and the second communication device, and information about a link connecting the second communication device and the third communication device; and, based on the acquired information, combining a first encrypted link for performing encrypted communication between the first communication device and the second communication device using a first key, and a second encrypted link for performing encrypted communication between the second communication device and the third communication device using a second key, thereby setting up an encrypted communication path from the first communication device to the third communication device.

[0098] 1 Network system 2 Optical network system 3, 3a, 3b Optical fiber 4 Optical network 10, 10a to 10d Node 11, 11a to 11c QKD transmitter 12, 12a to 12c QKD receiver 13, 13a to 13c Encoder 14, 14a to 14c Decoder 20 Optical network controller 21 Setting unit 22 Acquisition unit 30 Optical fiber 40 Computer 41 Processor 42 Memory 100 Transmission end node 110 Trusted node 111 QKD transmitter 112 Encoder 113 Optical transmitter 120 Multiplexer 130 Node control unit 200 Relay node 210 Trusted node 211 QKD receiver 212 Optical receiver 213 Decoder 214 QKD transmitter 215 Encoder 216 Optical transmitter 220 Demultiplexer 230 Multiplexer 240 Node control unit 300 Receiving end node 310 Trusted node 311 QKD receiver 312 Optical receiver 313 Decoder 320 Demultiplexer 330 Node control unit 400 Optical network controller 410 Management unit 420 Setting unit

Claims

1. A communication system comprising first, second, and third communication devices, and a control device for controlling the first, second, and third communication devices, wherein the first communication device includes first encryption means for encrypting data to be transmitted to the second communication device using a first key shared with the second communication device, the second communication device, includes first decryption means for decrypting data received from the first communication device using the first key, and second encryption means for encrypting data to be transmitted to the third communication device using a second key shared with the third communication device, the third communication device includes second decryption means for decrypting data received from the second communication device using the second key, and the control device includes setting means for connecting a first encryption link between the first encryption means and the first decryption means and a second encryption link between the second encryption means and the second decryption means to set an encrypted communication path from the first communication device to the third communication device. Communication system.

2. The first communication device includes first key distribution means for sharing the first key by performing quantum key distribution via a first key distribution link with the second communication device, the second communication device, includes second key distribution means for sharing the first key by performing the quantum key distribution via the first key distribution link with the first communication device, and third key distribution means for sharing the second key by performing the quantum key distribution via a second key distribution link with the third communication device, the third communication device includes fourth key distribution means for sharing the second key by performing the quantum key distribution via the second key distribution link with the second communication device, The communication system according to Claim 1.

3. The first communication device includes first multiplexing means for multiplexing a signal of the first encryption link and a signal of the first key distribution link and transmitting the multiplexed signal, the second communication device, includes first separation means for separating the multiplexed signal received from the first communication device into a signal of the first encryption link and a signal of the first key distribution link, and second multiplexing means for multiplexing a signal of the second encryption link and a signal of the second key distribution link and transmitting the multiplexed signal. The third communication device includes second separating means for separating the multiplexed signal received from the second communication device into the signal of the second encryption link and the signal of the second key delivery link. The communication system according to claim 2.

4. The first multiplexing means wavelength-division multiplexes the signal of the first encryption link and the signal of the first key delivery link. The second multiplexing means wavelength-division multiplexes the signal of the second encryption link and the signal of the second key delivery link. The communication system according to claim 3.

5. The setting means sets the wavelengths of the signals of the first encryption link and the second encryption link. The communication system according to claim 4.

6. The setting means extracts the first encryption link capable of encrypted communication from information on the link connecting the first communication device and the second communication device, extracts the second encryption link capable of encrypted communication from information on the link connecting the second communication device and the third communication device, and combines the extracted first encryption link and second encryption link. The communication system according to any one of claims 1 to 5.

7. A control device for controlling the first, second, and third communication devices, acquisition means for acquiring information on the link connecting the first communication device and the second communication device and information on the link connecting the second communication device and the third communication device; setting means for combining a first encryption link for performing encrypted communication between the first communication device and the second communication device using a first key and a second encryption link for performing encrypted communication between the second communication device and the third communication device using a second key based on the acquired information, and setting an encrypted communication path from the first communication device to the third communication device; A control device comprising the above.

8. A communication method in a communication system including first, second, and third communication devices and a control device for controlling the first, second, and third communication devices, The first communication device encrypts data to be transmitted to the second communication device using a first key shared with the second communication device. The second communication device decrypts the data received from the first communication device using the first key, encrypts the data to be transmitted to the third communication device using a second key shared with the third communication device. The third communication device decrypts data received from the second communication device using the second key. The control device couples a first encrypted link that performs encrypted communication between the first communication device and the second communication device using the first key and a second encrypted link that performs encrypted communication between the second communication device and the third communication device using the second key to set an encrypted communication path from the first communication device to the third communication device. Communication method.

9. A control method for controlling first, second, and third communication devices, obtaining information on a link connecting the first communication device and the second communication device and information on a link connecting the second communication device and the third communication device, based on the obtained information, coupling a first encrypted link that performs encrypted communication between the first communication device and the second communication device using a first key and a second encrypted link that performs encrypted communication between the second communication device and the third communication device using a second key to set an encrypted communication path from the first communication device to the third communication device. Control method.

10. A control program for controlling first, second, and third communication devices, obtaining information on a link connecting the first communication device and the second communication device and information on a link connecting the second communication device and the third communication device, based on the obtained information, coupling a first encrypted link that performs encrypted communication between the first communication device and the second communication device using a first key and a second encrypted link that performs encrypted communication between the second communication device and the third communication device using a second key to set an encrypted communication path from the first communication device to the third communication device. A control program for causing a computer to execute the process.